Actuator

ABSTRACT

An actuator includes a motor including a first rotor rotatable in a circumferential direction, and a stator to drive the first rotor; a second rotor rotatable in the circumferential direction; and a speed reducer that reduces rotation of the first rotor and transmits a torque to the second rotor via a bearing. The first and second rotors include first and second tube portions extending in an axial direction, respectively. The second tube portion is radially outward of the first tube portion. A lubricant is filled in a filling space including at least a portion of a space between an outer surface of the first tube portion and an inner surface of the second tube portion. The actuator includes a width reducing portion that reduces a width of the filling space in a radial direction in at least a portion of the filling space in the axial direction.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present disclosure relates to an actuator.

2. Description of the Related Art

In general, an articulated industrial robot is known. In such an industrial robot, an actuator is provided at a joint between a first arm and a second arm, in order to relatively rotatably connect the first arm and the second arm.

For example, Japanese Unexamined Patent Application Publication No. 2001-304382 discloses a hollow actuator having a lubricant leakage prevention mechanism which prevents lubricant leakage from a hollow wave gear device to a hollow AC servomotor, or to the outside.

In a lubricant leakage prevention mechanism, a gap between a hollow output shaft and a wave generator is covered with a lubricant separation member, and an opening of the gap extends to a position close to a wave bearing of the wave generator in order to suppress the lubricant leakage.

However, in Japanese Unexamined Patent Application Publication No. 2001-304382, the lubricant leakage prevention mechanism has a complicated structure, and thus the number of components in the hollow actuator also increases. Consequently, it is difficult to reduce or prevent increases in manufacturing cost, and also it is difficult to sufficiently improve production efficiency.

SUMMARY OF THE INVENTION

An actuator according to an exemplary embodiment of the present disclosure each include a motor including a first rotor rotatable in a circumferential direction about a center axis extending in a vertical direction, and a stator to drive the first rotor; a second rotor rotatable in the circumferential direction about the center axis; and a speed reducer which reduces rotation of the first rotor and transmits a torque to the second rotor, via a bearing, in which the first rotor includes a first tube portion extending in an axial direction, the second rotor includes a second tube portion extending in the axial direction, the second tube portion is provided radially outward of the first tube portion, a lubricant is filled in a filling space including at least a portion of a space between an outer surface of the first tube portion and an inner surface of the second tube portion, and the actuator further includes with a width reducing portion which reduces a width of the filling space in a radial direction in at least a portion of the filling space in the axial direction.

The above and other elements, features, steps, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating an exemplified configuration of an articulated robot.

FIG. 2 is a cross-sectional view illustrating an exemplified configuration of an actuator.

FIG. 3 is a cross-sectional view illustrating a first exemplified configuration of a width reducing portion.

FIG. 4 is a cross-sectional view illustrating a flow of a lubricant in the first exemplified configuration.

FIG. 5 is a cross-sectional view illustrating a modification example of the first exemplified configuration of the width reducing portion.

FIG. 6 is a cross-sectional view illustrating another modification example of the first exemplified configuration of the width reducing portion.

FIG. 7 is a cross-sectional view illustrating another example of an inclined portion and an inclined surface.

FIG. 8 is a cross-sectional view illustrating a second exemplified configuration of the width reducing portion.

FIG. 9 is a cross-sectional view illustrating a third exemplified configuration of the width reducing portion.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Exemplified embodiments of the present disclosure will be described below with reference to the drawings.

In this specification, a direction parallel to a center axis CA in an actuator 100 of an articulated robot R is referred to as the “axial direction”. Furthermore, in the axial direction, a direction from a cover 23 of a motor 110 toward a drive output portion 141 of a second rotor 140 is referred to as “upward”, while a direction from the drive output portion 141 of the second rotor 140 toward the cover 23 of the motor 110 is referred to as “downward”. Moreover, among surfaces of each component, a surface facing upward in the axial direction is referred to as “upper surface”, and a surface facing downward in the axial direction is referred to as “lower surface”.

A direction perpendicular to the center axis CA is referred to as “radial direction” and a circumferential direction about the center axis CA is referred to as “circumferential direction”. In the radial direction, a direction toward the center axis CA is referred to as “inward”, while a direction away from the center axis CA is referred to as “outward”. Moreover, among lateral surfaces of each component, a side surface facing inward in the radial direction is referred to as “inner surface”, and a side surface facing outward in the radial direction is referred to as “outer surface”.

It should be noted that the directions and surfaces stated above do not indicate the positional relationships, directions, etc., when incorporated in the actual device.

FIG. 1 is a perspective view illustrating an exemplified configuration of the articulated robot R. The articulated robot R is, for example, an industrial robot used in a manufacturing system for semiconductor devices. The articulated robot R includes a first arm R1, a second arm R2, a joint shaft R3, a base R4, and actuators 100 a to 100 c, as shown in FIG. 1. Additionally, the articulated robot R is provided with working units such as a gripping device or an imaging device for assembly, transportation, etc., however, those are not shown in FIG. 1.

The actuator 100 a is provided at one end of the first arm R1. A working unit (not shown) is also attached to the actuator 100 a. That is, the actuator 100 a is provided at a first joint portion between the working unit and the one end of the first arm R1. The actuator 100 b is provided at a second joint portion between the other end of the first arm R1 and one end of the second arm R2. The actuator 100 c is provided at a third joint portion between the other end of the second arm R2 and one end of the joint shaft R3. In the second arm R2, one end fixed to the actuator 100 b is bent perpendicular to the other end fixed to the actuator 100 c. The other end of the joint shaft R3 is fixed to the base R4 for installing the articulated robot R.

The first arm R1, the second arm R2 and the working unit rotate relative to the joint shaft R3 and the base R4 by driving respective actuators 100 a, 100 b and 100 c. That is, the working unit rotates about a rotation axis of the actuator 100 a with respect to the first arm R1 by driving the actuator 100 a at the first joint portion. The first arm R1, the actuator 100 a and the working unit rotate about a rotation axis of the actuator 100 b with respect to the second arm R2 by driving the actuator 100 b at the second joint portion. Furthermore, the first arm R1, the second arm R2, the actuators 100 a and 100 b, and the working unit rotate about a rotation axis of the actuator 100 c with respect to the joint shaft R3 by driving the actuator 100 c at the third joint portion.

The actuators 100 a, 100 b and 100 c of the respective joint portions will be collectively referred to as the actuator 100 hereinbelow. In this case, the center axis CA (refer to FIG. 2 described later) of the actuator 100 corresponds to the rotational axes of the actuators 100 a, 100 b and 100 c. Moreover, in this embodiment, the actuator 100 is provided at the first to third joint portions of the articulated robot R, however, the application of the actuator 100 is not limited to this example.

FIG. 2 is a cross-sectional view illustrating an exemplified configuration of the actuator 100. In FIG. 2, the actuator 100 is cut with a cutting plane including the center axis CA. The actuator 100 is provided with a motor 110, a speed reducer 120, a cross-roller bearing 130, a second rotor 140, and a second bearing 150, as shown in FIG. 2.

First, a configuration of the motor 110 will be described. The motor 110 includes a first rotor 1, a stationary portion 2, a first bearing 3, a lubricant 4, and a width reducing portion 5. The motor 110 further includes a stator 21 (described below) for driving the first rotor 1. The motor 110 is an outer rotor type, and is a driving source of the actuator 100.

The first rotor 1 is rotatable in the circumferential direction about the center axis CA extending in the vertical direction. The first rotor 1 includes a tubular first tube portion 11, a circular plate portion 12 having an annular shape, a tubular magnet holding member 13, and a rotor magnet 14. The first tube portion 11 extends in the axial direction to face a post portion 201 of a shaft 20 (described later) in the radial direction. Moreover, the first tube portion 11 has a protrusion portion 11 a. The protrusion portion 11 a is provided at a connecting part between the first tube portion 11 and the circular plate portion 12. The protrusion portion 11 a is, for example, a step that protrudes from the circular plate portion 12. The circular plate portion 12 extends outward in the radial direction from a lower portion of the first tube portion 11 in the axial direction. The magnet holding member 13 extends downward in the axial direction from an outer peripheral portion of the circular plate portion 12 in the radial direction, thereby holding the rotor magnet 14. The rotor magnet 14 is held on an inner surface of the magnet holding member 13, faces the stator 21 in the radial direction, and is rotatable together with the first rotor 1 in the circumferential direction. The rotor magnet 14 is disposed facing an outer surface of the stator 21 in the radial direction. In particular, a plurality of different magnetic poles are alternately arranged on the inner surface of the magnet holding member 13 in the circumferential direction.

The stationary portion 2 rotatably supports the second rotor 140 via the cross-roller bearing 130 and the second bearing 150. The stationary portion 2 includes a shaft 20, a stator 21, a bracket 22, a cover 23, a substrate 24, a cable 25, a sensor 26, and flexible printed circuits (FPC) 27.

The shaft 20 is a fixed shaft. The shaft 20 includes a through-hole 20 a penetrating in the axial direction. In particular, the through-hole 20 a is a space that penetrates the post portion 201, as well as a disk portion 2021 and a tube portion 2022 of a lid portion 202, as described below.

Furthermore, the shaft 20 includes the post portion 201 extending along the center axis CA and the lid portion 202 provided at one end (upper end) of the post portion 201 in the axial direction. The post portion 201 is a cylindrical hollow member penetrated by the through-hole 20 a. Moreover, the post portion 201 and the lid portion 202 may be different members provided separately from each other as shown in FIG. 2, but may be coupled to each other to form a single member.

The lid portion 202 includes the disk portion 2021 and the tube portion 2022. The disk portion 2021 extends radially outward from the post portion 201 when viewed from the axial direction. The tube portion 2022 extends downward in the axial direction from an inner peripheral portion of the disk portion 2021 in the radial direction. The tube portion 2022 extends from the disk portion 2021 toward the post portion 201 in the axial direction, and is coupled to one end of the post portion 201 in the axial direction. The inner diameter of a lower portion of the tube portion 2022 in the axial direction is slightly larger than the outer diameter of an upper portion of the post portion 201 in the axial direction. Therefore, the tube portion 2022 is coupled to the upper portion of the post portion 201 in the axial direction by fitting the upper portion of the post portion 201 in the axial direction into the lower portion of the tube portion 2022 in the axial direction.

The stator 21 faces the magnet holding member 13 of the first rotor 1 in the radial direction to drive the first rotor 1. The bracket 22 is a member accommodating the stator 21 therein and holding the stator 21. The bracket 22 includes a wall portion 221 as shown in FIG. 2. In particular, the motor 110 includes the wall portion 221, and the wall portion 221 faces, radially outward of the magnet holding member 13, the magnet holding member 13 in the radial direction. The cover 23 accommodates the stator 21 and a lower portion of the substrate 24 in the axial direction, and is attached to the bracket 22. Furthermore, the covers 23 are, for example, fixed to the first arm R1, the second arm R2 and the joint shaft R3, at the first to third joint portions of the articulated robot R (see FIG. 1), respectively. In particular, the cover 23 of the actuator 100 a is fixed to one end of the first arm R1. The cover 23 of the actuator 100 b is fixed to one end of the second arm R2. The cover 23 of the actuator 100 c is fixed to one end of the joint shaft R3.

The substrate 24 is attached to a lower surface of the bracket 22 at a lower end of the motor 110 in the axial direction. In particular, the substrate 24 is provided on a side opposite to the sensor 26 with the post portion 201 interposed therebetween in the axial direction. The substrate 24 is electrically connected to the stator 21, and further electrically connected to the sensor 26 via a cable 25 and an FPC 27. The substrate 24 carries a control circuit (not shown), a communication circuit (not shown), and the like. The control circuit has functions of performing drive control of the motor 110, and controlling a rotational position of the second rotor 140. The communication circuit contains an input/output terminal complying with, for example, the Ethernet standard, and has a function of communicating with a device outside the actuator 100. Therefore, it is possible to control the actuator 100 using an external device connected to the communication circuit.

The cable 25 is a wiring passing inside the through-hole 20 a, and electrically connects the sensor 26 and the substrate 24. Consequently, the sensor 26 for detecting a rotational position of a sensor magnet 146 (described later) is connected to the substrate 24 via the cable 25 communicating inside of the through-hole 20 a in the axial direction, which penetrates the shaft 20 and the post portion 201 in the axial direction. Accordingly, the cable 25, which electrically connects the sensor 26 and the substrate 24, does not have to pass through, for example, outside of the stationary portion 2, radially outward of the shaft 20 in the radial direction. Therefore, the actuator 100 can be downsized in the radial direction.

The sensor 26 is, for example, a Hall element, which is provided on the lid portion 202. The sensor 26 faces a portion of a trajectory of the sensor magnet 146 rotating in the circumferential direction to detect a rotational position of the sensor magnet 146. The sensor 26 may be at a position in the axial direction facing a portion of the trajectory of the sensor magnet 146 rotating in the circumferential direction, or at a position in the radial direction facing a portion of the trajectory of the sensor magnet 146 rotating in the circumferential direction, as shown in FIG. 2.

The FPC 27 is a bendable printed circuit board on which the sensor 26 is mounted, and is affixed to the lower surface of the disk portion 2021.

The first bearing 3 is provided between the first rotor 1 and the shaft 20 of the stationary portion 2. In particular, the first bearing 3 is provided between the first tube portion 11 and the post portion 201. The first bearing 3 rotatably supports the first rotor 1 with respect to the stationary portion 2. For example, a ball bearing can be used as the first bearing 3. The first bearing 3 is fixed to the first rotor 1, and to the post portion 201 of the shaft 20 provided in the stationary portion 2, as shown in FIG. 2. In particular, an inner ring of the first bearing 3 is fixed to an outer surface of the post portion 201. Meanwhile, an outer ring of the first bearing 3 is fixed to an inner surface of the first tube portion 11 of the first rotor 1.

The first bearing 3 is disposed above a magnetic circuit of the motor 110 in the axial direction, which includes the rotor magnet 14, the stator 21, etc., and does not overlap with the magnetic circuit in the radial direction. Therefore, it is possible to downsize the actuator 100 by increasing a size in the radial direction of the magnetic circuit of the motor 110, or decreasing a size in the radial direction of the actuator 100, as compared with a case where the first bearing 3 overlaps with the magnetic circuit in the radial direction.

The lubricant 4 is, for example, grease, and is filled in a filling space S including at least a portion of a space between an outer surface of the first tube portion 11 and an inner surface of a second tube portion 143.

The width reducing portion 5 reduces a width of the filling space S in the radial direction in at least a portion of the filling space S in the axial direction. Consequently, a flow of the lubricant 4 leaking from the filling space S to the outside is suppressed by the width reducing portion 5. Accordingly, it is possible to reduce the lubricant 4 leaking from the filling space S to the outside. Therefore, it is possible to suppress leakage of the lubricant 4 with a simple configuration.

The width reducing portion 5 includes at least one of a sealing member 51 and a gap member 52. The sealing member 51 is in the shape of a plate extending in the radial direction and annular when viewed from the axial direction. In FIG. 2, the sealing member 51 forms a first gap S1 with the first tube portion 11. The gap member 52 is annular when viewed from the axial direction. The gap member 52 forms a second gap S2 with the second tube portion 143 in FIG. 2. In particular, the gap member 52 forms the second gap S2 with a hat gear 122. A configuration of the width reducing portion 5 will be described later.

A configuration of the speed reducer 120 will be described below. The speed reducer 120 reduces the rotation of the first rotor 1 and transmits the torque to the second rotor 140 via an elastic bearing 124. In this embodiment, Flexwave (registered trademark, manufactured by Nidec-Shimpo Corporation), which is a wave gear device having a reduction ratio of 1/100, is adopted as the speed reducer 120, but the present disclosure is not limited to the example of the embodiment. Other reducer such as a planetary gear device may be used as the speed reducer 120 of the actuator 100.

The speed reducer 120 includes an internal gear 121, a hat gear 122, a cam 123, and an elastic bearing 124, as shown in FIG. 2.

The internal gear 121 is an internal gear having rigidity, in which teeth aligned in the circumferential direction are formed on an inner surface in the radial direction. The internal gear 121 is connected to an inner ring of the cross-roller bearing 130 and a drive output portion 141 (described later) of the second rotor 140, and is rotatable together with those components in the circumferential direction.

The hat gear 122 includes a cylindrical portion extending in the axial direction, and an annular portion covering an upper end of the cylindrical portion in the axial direction. The post portion 201 of the shaft 20 is inserted into an opening provided at the center of the annular portion. The cylindrical portion of the hat gear 122 is deformable in the radial direction. An outer surface of the cylindrical portion in the radial direction has teeth formed in the circumferential direction. The number of the teeth is smaller than the number of the teeth formed on an inner surface of the internal gear 121.

The cam 123 has an elliptical shape when viewed from the axial direction, and is fixed to the first rotor 1 so as to be rotatable together with the first rotor 1. The cam 123 is formed with an opening penetrating in the axial direction at its center. The cam 123 is rotatable about the center axis CA with respect to the post portion 201 by inserting the post portion 201 of the shaft 20 into the opening of the cam 123.

The elastic bearing 124 is a radially deformable bearing, and is provided on an outer surface of the cam 123 along an outer peripheral portion of the elliptical cam 123. The elastic bearing 124 is held by the first rotor 1 radially outward of the first bearing 3, and rotatably supports the second rotor 140. An inner ring of the elastic bearing 124 is fixed to the cam 123, is attached to the first rotor 1 via the cam 123, and is rotatable together with the first rotor 1 in the circumferential direction.

The elastic bearing 124 is accommodated inside the cylindrical portion of the hat gear 122, and deforms the cylindrical portion of the hat gear 122 in the radial direction in response to a shape of the cam 123. In particular, the elastic bearing 124 deflects the cylindrical portion of the hat gear 122 by pushing the cylindrical portion in the radial direction, so that the teeth formed on an outer surface of the deflected portion are partially engaged with the teeth formed on the inner surface of the internal gear 121. Furthermore, the elastic bearing 124 moves a position at which the hat gear 122 and the internal gear 121 are partially engaged in the circumferential direction by rotating the elastic bearing 124 together with the first rotor 1. At this time, the internal gear 121 having more teeth than the hat gear 122 rotates at a lower speed than that of the hat gear 122 in response to a difference between the number of teeth of hat gear 122 and the number of teeth of the internal gear 121. Accordingly, the speed reducer 120 rotates the second rotor 140 connected to the internal gear 121 at a lower speed than that of the first rotor 1 inputting the driving force of the elastic bearing 124 and the hat gear 122.

A configuration of the second rotor 140 will be described. The second rotor 140 is rotatable about the center axis CA in the circumferential direction. The second rotor 140 includes a drive output portion 141, a rotation transmission portion 142, a tubular second tube portion 143, a rotor support portion 144, a magnet support portion 145, and a sensor magnet 146.

The drive output portions 141 are connected to the working unit, the first arm R1 and the second arm R2, at the first to third joint portions of the articulated robot R (see FIG. 1), respectively. The drive output portions 141 output the driving force of the actuator 100 to the working unit, the first arm R1 and the second arm R2. In particular, the drive output portion 141 of the actuator 100 a is connected to the working unit and outputs the driving force to the working unit. The drive output portion 141 of the actuator 100 b is connected to the first arm R1 and outputs the driving force to the first arm R1. The drive output portion 141 of the actuator 100 c is connected to the second arm R2 and outputs the driving force to the second arm R2.

The rotation transmission portion 142 is connected to the drive output portion 141 and the second tube portion 143, and is rotatable together with the drive output portion 141 and the second tube portion 143 in the circumferential direction. The rotation transmission portion 142 transmits the driving force, input from the first rotor 1 and reduced in the rotation speed by the speed reducer 120, to the second rotor 140 (in particular, the drive output portion 141). The rotation transmission portion 142 is the same member as the internal gear 121 of the speed reducer 120 in this embodiment. That is, the internal gear 121 functions as the rotation transmission portion 142. However, the rotation transmission portion 142 is not limited to this example, and may be a different member from the internal gear 121. In a case where the rotation transmission portion 142 is a different member, the rotation transmission portion 142 is connected to the internal gear 121.

The second tube portion 143 extends in the axial direction, and is provided radially outward of the first tube portion 11. The second tube portion 143 is connected to the rotation transmission portion 142. The second tube portion 143 is the same member as the inner ring of the cross-roller bearing 130 in this embodiment. That is, the inner ring of the cross-roller bearing 130 functions as the second tube portion 143. However, the second tube portion 143 is not limited to this example, and may be a different member from the inner ring of the cross-roller bearing 130. In a case where the second tube portion 143 is a different member, the second tube portion 143 is connected to the inner ring of the cross-roller bearing 130.

The rotor support portion 144 positions an attachment position of the second bearing 150 to the drive output portion 141. Moreover, the magnet support portion 145 supports the sensor magnet 146. The sensor magnet 146 is provided on the second rotor 140 and is rotatable together with the second rotor 140 in the circumferential direction. In this embodiment, the sensor magnet 146 is provided with different magnetic poles formed alternately in the circumferential direction, and is disposed facing the sensor 26 in the radial direction. However, the sensor magnet 146 is not limited to the example of this embodiment, and may be configured to have a plurality of magnet pieces having different magnetic poles alternately arranged in the circumferential direction.

A configuration of the width reducing portion 5 will be described with reference to first to third exemplified configurations.

First, a first exemplified configuration of the width reducing portion 5. FIG. 3 is a cross-sectional view illustrating the first exemplified configuration of the width reducing portion 5. FIG. 3 corresponds to a part surrounded by a broken line in FIG. 2. In the first exemplified configuration, the width reducing portion 5 includes the sealing member 51 and the gap member 52 as shown in FIG. 3.

The sealing member 51 is provided at an upper end of the wall portion 221 of the bracket 22 in the axial direction, and extends radially inward from the upper end of the wall portion 221. In a case where the width reducing portion 5 includes at least the sealing member 51, an outer end of the sealing member 51 in the radial direction is provided on the wall portion 211; in particular, the outer end of the sealing member 51 is fixed to an upper surface of the wall portion 211. An inner end of the sealing member 51 in the radial direction faces the first tube portion 11, and forms a minute first gap S1 with the outer surface of the first tube portion 11 in the radial direction. Moreover, a gap between the sealing member 51 and the first tube portion 11 in the axial direction (that is, the shortest distance therebetween, and a width W of the first gap S1 in the radial direction) is, for example, 0.05 mm. It is possible to suppress a flow of the lubricant 4 leaking from the filling space S to the outside by providing the sealing member 51 in the filling space S. Even though the sealing member 51 is provided in the filling space S, the volume of the filling space S is not reduced so much. Therefore, leakage of the lubricant 4 can be suppressed without significantly reducing a filling amount of the lubricant 4 in the filling space S.

The gap member 52 is provided on the first tube portion in FIG. 3. A position of the gap member 52 in the axial direction is determined by the protrusion portion 11 a. In particular, when the gap member 52 is provided on the first tube portion 11, a lower end of the gap member 52 in axial direction is in contact with an upper surface of the protrusion portion 11 a, thereby positioning the gap member 52 in the axial direction. Moreover, the protrusion portion 11 a is coupled with the first tube portion 11 in FIG. 3, but is not limited to this example. The protrusion portion 11 a may not be coupled with the first tube portion 11. That is, the protrusion portion 11 a may protrude axially upward from the circular plate portion 12 at a position away from the first tube portion 11 in the radial direction.

The gap member 52 includes an inclined portion 521 upward in the axial direction. The inclined portion 521 of the gap member 52 includes, axially upward, an inclined surface 521 a intersecting the axial direction. In FIG. 3, an outer peripheral edge of the inclined surface 521 a on a side of the second tube portion 143 is disposed axially upward of an inner peripheral edge of the inclined surface 521 a on a side of the first tube portion 11. In particular, an upper portion of the gap member 52 in the axial direction is the inclined portion 521, and an upper surface of the gap member 52 toward the elastic bearing 124 is the inclined surface 521 a. Consequently, the gap member 52 having the inclined surface 521 a can be easily manufactured. A shape of the gap member 52 is simple, thus a strength of the gap member 52 can be enhanced as compared with a case where such a shape is complicated.

In the first exemplified configuration, the lubricant 4 filled in the filling space S flows through a space having a labyrinth structure established by the sealing member 51 and the gap member 52. FIG. 4 is a cross-sectional view illustrating a flow of the lubricant 4 in the first exemplified configuration. As shown in FIG. 4, the sealing member 51 forms the first gap S1, and the gap member 52 forms the second gap S2. Furthermore, the sealing member 51 is provided between the gap member 52 and the circular plate portion 12 of the first rotor 1 in the axial direction. Consequently, a labyrinth structure space can be formed in the filling space S filled with the lubricant 4. The lubricant 4 flows through the labyrinth structure space when flowing from the filling space S to the outside. In particular, the lubricant 4 needs to pass through the second gap S2 formed by the annular gap member 52, a space between the annular sealing member 51 and the annular gap member 52, the first gap S1 between the inner end of the annular sealing member 51 in the radial direction and the first tube portion 11, and a space between the annular sealing member 51 and the circular plate portion 12 having the annular shape. Accordingly, the lubricant 4 hardly flows from the filling space S to the outside. Therefore, it is possible to further suppress leakage of the lubricant 4.

The outer end of the sealing member 51 in the radial direction is not limited to the examples of FIGS. 3 and 4, and may be provided at a lower end of the hat gear 122 provided in the speed reducer in the axial direction. That is, in a case where the width reducing portion 5 includes at least the sealing member 51, the outer end of the sealing member 51 in the radial direction may be provided on the speed reducer 120.

In a case where the second tube portion 143 directly faces the filling space S and is directly in contact with the lubricant 4, the gap member 52 may be provided on the second tube portion 143. FIG. 5 is a cross-sectional view illustrating a modification example of the first exemplified configuration of the width reducing portion 5. FIG. 5 corresponds to a part surrounded by a broken line in FIG. 2. The gap member 52 provided on the second tube portion 143 forms a third gap S3 with the first tube portion 11 as shown in FIG. 5. Furthermore, the inner peripheral edge of the inclined surface 521 a of the inclined portion 521 on a side of the first tube portion 11 is axially upward of the outer peripheral edge of the inclined surface 521 a on a side of the second tube portion 143, as shown in FIG. 5.

As stated above, the gap member 52 may be provided on one member of the first tube portion 11 and the second tube portion 143. The gap member 52 forms the second gap S2 or the third gap S3 with the other member of the first tube portion 11 and the second tube portion 143 in the radial direction. By providing the gap member 52 in the filling space S, the longer the second gap S2 in the axial direction is, the harder the lubricant 4 flowing through the second gap S2 or the third gap S3 flows. Therefore, it is possible to suppress flow of the lubricant 4 leaking from the filling space S to the outside according to the length of the second gap S2 or the third gap S3 in the axial direction.

In a case where the second tube portion 143 directly faces the filling space S and is directly in contact with the lubricant 4, as shown in FIG. 5, a protrusion portion 143 a may be provided on the second tube portion 143 to position the gap member 52 in the axial direction. The protrusion portion 143 a protrudes in the radial direction from the second tube portion 143 toward the first tube portion 11. When providing the gap member 52 on the second tube portion 143, a lower end of the gap member 52 in the axial direction is in contact with an upper surface of the protrusion portion 143 a, thereby positioning the gap member 52 in the axial direction.

As state above, one member of the first tube portion 11 and the second tube portion 143 may include a protrusion portion 11 a or 143 a which protrudes toward the other member in the radial direction. In this case, the gap member 52 is in contact with the protrusion portion 11 a or 143 a in the axial direction. Consequently, a position of the gap member 52 in the axial direction is determined by the protrusion portion 11 a or 143 a. In particular, the lower end of the gap member 52 in the axial direction is in contact with an upper surface of the protrusion portion 11 a or 143 a, thus the gap member 52 is positioned in the axial direction by the protrusion portion 11 a or 143 a. Therefore, the gap member 52 can be attached more easily, and the attachment work can be carried out with the improved efficiency.

Furthermore, in a case where the second tube portion 143 directly faces the filling space S and is directly in contact with the lubricant 4, the outer end of the sealing member 51 in the radial direction may be provided at a lower end of the second tube portion 143 in the axial direction. That is, in a case where the width reducing portion 5 includes at least the sealing member 51, the outer end of the sealing member 51 in the radial direction may be provided on the second tube portion 143.

In the configuration where the sealing member 51 and the gap member 52 are provided on the second tube portion 143, the speed reducer 120 may be, for example, a planetary speed reducer other than the wave gear device.

The gap member 52 is a member different from one member of the first tube portion 11 and the second tube portion 143 in FIGS. 3 to 5. However, the configuration of the gap member 52 is not limited to these examples. FIG. 6 is a cross-sectional view illustrating another modification example of the first exemplified configuration of the width reducing portion 5. FIG. 6 corresponds to a part surrounded by a broken line in FIG. 2. In a case where the width reducing portion 5 includes at least the gap member 52 as shown in FIG. 6, the gap member 52 may be integrally formed with one of the first tube portion 11 and the second tube portion 143. In particular, the gap member 52 provided on the first tube portion 11 may form a single member with the first tube portion 11, and in other words, may be a portion of the first tube portion 11, as shown in FIG. 6. The gap member 52 provided on the second tube portion 143 may form a single member with the second tube portion 143, and in other words, may be a portion of the second tube portion 143. Consequently, the number of components in the actuator 100 can be decreased, thus it is possible to suppress increase in manufacturing cost, and to sufficiently improve production efficiency. Moreover, the gap member 52 may be made of the same material as that of one member of the first tube portion 11 and the second tube portion 143, or a different material from that of the one member.

In the gap member 52, a peripheral edge of the inclined surface 521 a of the inclined portion 521 in the radial direction on a side of one member of the first tube portion 11 and the second tube portion 143 is closer to a side of the elastic bearing 124 in the axial direction than a peripheral edge on a side of the other member. Furthermore, as illustrated in FIGS. 3 to 5, an inclination angle θ of the inclined surface 521 a with respect to the axial direction from the gap member 52 toward the elastic bearing 124 is an acute angle. Consequently, the lubricant 4 hardly flows toward the second gap S2 or the third gap S3 by the inclined surface 521 a. Therefore, it is possible to further suppress leakage of the lubricant 4.

In FIGS. 3 to 6, the entire upper surface of the gap member 52 in the axial direction is the inclined surface 521 a. However, the configuration of the inclined surface 521 a is not limited to these examples. The inclined portion 521 may be a portion of the upper portion of the gap member 52 in the axial direction. Furthermore, the inclined surface 521 a may be a portion of an upper surface of the inclined portion 521. FIG. 7 is a cross-sectional view illustrating another example of the inclined portion 521 and the inclined surface 521 a. FIG. 7 corresponds to a part surrounded by a broken line in FIG. 2.

As shown in FIG. 7, the inclined portion 521 may be a portion of the upper portion of the gap member 52 in the axial direction. Furthermore, the inclined portion 521 may protrude axially upward from the upper surface of the gap member 52; in particular, the inclined portion 521 may protrude axially upward from a partial region of the upper surface in the radial direction. The inclined portion 521 may extend in the circumferential direction, and is preferably annular. In this case, the inclined portion 521 overlaps with the upper surface of the gap member 52 when viewed from the axial direction. The upper surface is a surface of the gap member 52 toward the elastic bearing 124. “Axially upward” means a side of the elastic bearing 124 in the axial direction. Consequently, the volume of the filling space S reduced by the gap member 52 is smaller as compared with a case where the upper surface of the gap member 52 is the inclined surface 521 a. Additionally, the lubricant 4 hardly flows to the second gap S2 by the inclined surface 521 a. Therefore, it is possible to further suppress leakage of the lubricant 4 while suppressing reduction of the amount of the lubricant 4 fillable in the filling space S.

A position of the inclined portion 521 in the radial direction in the upper surface of the gap member 52 is radially outward of an inner surface of the gap member 52. Such a position may also be radially inward of an outer surface of the gap member 52, and preferably overlaps with the inner surface or the outer surface of the gap member 52 when viewed from the axial direction. In particular, the peripheral edge of the inclined surface 521 a preferably overlaps with a peripheral edge of the gap member 52 in, rather than a side of one member of the of the first tube portion 11 and the second tube portion 143, a side of the other member in the radial direction, when viewed from the axial direction. That is, in a case where the gap member 52 is provided on the first tube portion 11, the peripheral edge of the inclined surface 521 a preferably overlaps with an outer peripheral edge of the gap member 52, radially outward, i.e., closer to a side of the second tube portion 143 than a side of the first tube portion 11 in the radial direction, when viewed from the axial direction. In a case where the gap member 52 is provided on the second tube portion 143, the peripheral edge of the inclined surface 521 a preferably overlaps with an inner peripheral edge of the gap member 52, radially inward, i.e. closer to a side of the first tube portion 11 than a side of the second tube portion 143 in the radial direction, when viewed from the axial direction. Consequently, the lubricant 4 further hardly flows toward the second gap S2 or the third gap S3.

The width reducing portion 5 includes both of the sealing member 51 and the gap member 52 in the first exemplified configuration. However, the width reducing portion 5 is not limited to the example of the first exemplified configuration, and may be configured to include one of the sealing member 51 and the gap member 52 without the other one.

FIG. 8 is a cross-sectional view illustrating a second exemplified configuration of the width reducing portion 5. FIG. 8 corresponds to a part surrounded by a broken line in FIG. 2. In the second exemplified configuration, the width reducing portion includes the sealing member 51 but does not include the gap member 52, as shown in FIG. 8. Additionally, the outer end of the sealing member 51 in the radial direction is provided on the wall portion 221 as shown in FIG. 8.

Alternatively, the outer end of the sealing member 51 in the radial direction is not limited to the example of FIG. 8, and may be provided on one of the speed reducer 120 or the second tube portion 143. In particular, the outer end of the sealing member 51 in the radial direction may be provided at the lower end of the hat gear 122 of the speed reducer 120. Furthermore, in a case where the second tube portion 143 directly faces the filling space S and is directly in contact with the lubricant 4, the outer end of the sealing member 51 in the radial direction may be provided on a lower portion of the second tube portion 143 in the axial direction.

In the second exemplified configuration, the lubricant 4 needs to pass through, when flowing from the filling space S to the outside, the first gap S1 between the inner end of the annular sealing member 51 in the radial direction and the first tube portion 11, and a space between the annular sealing member 51 and the circular plate portion 12 having the annular shape. Accordingly, the lubricant 4 hardly flows from the filling space S to the outside as compared with a configuration where the sealing member 51 is not provided on the actuator 100. Therefore, it is possible to suppress leakage of the lubricant 4 by the sealing member 51.

FIG. 9 is a cross-sectional view illustrating a third exemplified configuration of the width reducing portion 5. FIG. 9 corresponds to a part surrounded by a broken line in FIG. 2. In the third exemplified configuration, the width reducing portion 5 includes at least the gap member 52, as shown in FIG. 9. The gap member 52 is provided on the first tube portion 11 and is in contact with the circular plate portion 12. Furthermore, the gap member 52 forms the second gap S2 with the second tube portion 143 in the radial direction. In particular, the gap member 52 forms the second gap S2 with the cylindrical portion of the hat gear 122 extending in the axial direction. Consequently, it is possible to position the gap member 52 in the axial direction by the circular plate portion 12 of the first rotor 1. Therefore, the gap member 52 can be attached more easily, and the attachment work can be carried out with the improved efficiency.

In the third exemplified configuration, the lubricant 4 needs to pass through, when flowing from the filling space S to the outside, the second gap S2 formed by the annular gap member 52. Accordingly, the lubricant 4 hardly flows from the filling space S to the outside as compared with a configuration where the width reducing portion 5 is not provided on the actuator 100. Therefore, it is possible to suppress leakage of the lubricant 4 by the gap member 52.

The embodiments of the present disclosure have been described above. The scope of the present disclosure is not limited to the embodiments stated above. Features of the above-described preferred embodiments and the modifications thereof may be combined appropriately as long as no conflict arises.

While preferred embodiments of the present disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The scope of the present disclosure, therefore, is to be determined solely by the following claims.

The present disclosure is useful for an actuator attached to the robot or the like. 

1-14. (canceled)
 15. An actuator comprising: a motor including a first rotor rotatable in a circumferential direction about a center axis extending in a vertical direction, and a stator to drive the first rotor; a second rotor rotatable in the circumferential direction about the center axis; and a speed reducer that reduces rotation of the first rotor and transmits a torque to the second rotor, via a bearing; wherein the first rotor includes a first tube portion extending in an axial direction; the second rotor includes a second tube portion extending in the axial direction; the second tube portion is radially outward of the first tube portion; a lubricant is filled in a filling space including at least a portion of a space between an outer surface of the first tube portion and an inner surface of the second tube portion; and the actuator further comprises a width reducing portion that reduces a width of the filling space in a radial direction in at least a portion of the filling space in the axial direction.
 16. The actuator according to claim 15, wherein the width reducing portion includes at least one of a seal and a gap; the seal has a plate shape extending in the radial direction and annular when viewed from the axial direction; an inner end of the seal in the radial direction faces the first tube portion and defines a first gap with an outer surface of the first tube portion in the radial direction; and the gap is annular when viewed from the axial direction, is provided on at least one of the first tube portion and the second tube portion, and defines a second gap with the other of the first tube portion and the second tube portion in the radial direction.
 17. The actuator according to claim 16, wherein the width reducing portion includes at least the seal; the motor includes a rotor magnet facing the stator, a magnet holder that holds the rotor magnet, and a wall radially facing the magnet holder radially outward of the magnet holder; and an outer end of the seal in the radial direction is provided on the wall portion.
 18. The actuator according to claim 16, wherein the width reducing portion includes at least the seal; and an outer end of the seal in the radial direction is provided on one of the speed reducer and the second tube portion.
 19. The actuator according to claim 16, wherein the width reducing portion includes at least the gap; and the gap is integral with one of the first tube portion and the second tube portion.
 20. The actuator according to claim 16, wherein the one of the first tube portion and the second tube portion includes a protrusion that protrudes toward the other of the first tube portion and the second tube portion in the radial direction; and the gap is in contact with the protrusion in the axial direction.
 21. The actuator according to claim 16, wherein the first rotor further includes a circular plate portion extending radially outward from the first tube portion; the width reducing portion includes at least the gap; and the gap is provided on the first tube portion and is in contact with the circular plate portion to define the second gap with the second tube portion in the radial direction.
 22. The actuator according to claim 20, wherein the protrusion includes a step that protrudes from the circular plate portion in the axial direction.
 23. The actuator according to claim 16, wherein the first rotor further includes a circular plate portion extending radially outward from the first tube portion; the width reducing portion includes the seal and the gap; and the seal is provided between the gap and the circular plate portion in the axial direction.
 24. The actuator according to claim 16, wherein the gap includes an inclined portion; and in the inclined portion, a peripheral edge, of an inclined surface, on a side of the one of the first tube portion and the second tube portion in the radial direction is closer to a side of the bearing than a peripheral edge on a side of the other of the first tube portion and the second tube portion in the axial direction.
 25. The actuator according to claim 24, wherein an inclination angle of the inclined surface with respect to the axial direction from the gap toward the bearing is an acute angle.
 26. The actuator according to claim 24, wherein a surface of the gap facing the bearing defines the inclined surface.
 27. The actuator according to claim 24, wherein the inclined portion protrudes from a surface of the gap facing the bearing toward a side of the bearing in the axial direction; and the inclined portion overlaps with a portion of the surface of the gap facing the bearing when viewed from the axial direction.
 28. The actuator according to claim 27, wherein a peripheral edge of the inclined surface overlaps with a peripheral edge of the gap on a side of the other of the first tube portion and the second tube portion instead of the one of the first tube portion and the second tube portion in the radial direction, when viewed from the axial direction. 